The present invention relates generally to sharpening machines for saws and more specifically relates to sharpening machines for saws wherein a carrier is tiltable to different orientations.
Sharpening machines of this sort generally include a mount for a saw blade and a tiltable carrier which is adapted to be tilted about an axis of tilt oriented perpendicular to the plane of a saw blade. A support which is movably secured to the carrier is arranged so as to swivel relative to the carrier through at least 180.degree. about a swivel axis lying in the plane of the saw blade. A lifting device provides for reciprocal movement of the support along the swivel axis. A grinding head is connected to the support and carries a grinding wheel whose active face is contiguous with the swivel axis. The orientation of the grinding wheel with respect to a saw tooth may be adjusted to accommodate the sharpening of various sized saw teeth by moving the above-mentioned components relative to one another.
In a known sharpening machine for saws, such as is disclosed in DE-OS No. 26 14 419 and corresponding U.S. Pat. No. 4,136,585 of Lenard, the swivel axis of the grinding head intersects the axis of tilt of the carrier at right angles. The grinding head can be swiveled about the swivel axis by 45.degree. to one side and by 225.degree. (i.e. 180.degree. plus 45.degree.) to the other side.
In a further development of this known sharpening machine for saws as disclosed in German OS No. 27 51 408, a swiveling device for the grinding head includes a shaft whose geometric axis constitutes the swivel axis of the grinding head and whose range of swivel from the standard position is less than 90.degree. in both directions of swivel. The grinding head is attached to the shaft in one of two positions which are offset by 180.degree..
In both of the above-mentioned sharpening machines for saws, a grinding wheel spindle is mounted to the grinding head. A plate-shaped grinding wheel having an operating or active face is attached in two different selected orientations at one end of the grinding wheel spindle. In a first orientation, the face is turned to the grinding head and in a second orientation, the face is turned away from the grinding head. The first orientation is suitable, by way of example, for grinding faces (cutting edges of teeth) having a positive rake angle, and the second orientation is suitable for grinding flanks at the back of teeth and/or faces having a negative rake angle.
In the known machines of this type, it is possible for all faces to be ground in the first orientation of the grinding wheel during the first revolution of the saw blade. The grinding wheel is then detached from the grinding wheel spindle and turned around or replaced by another grinding wheel, which is attached to the spindle in such a way that its operating face is turned away from the grinding head. In this manner, all the flanks on the back of the teeth can be ground. Turning around or replacing the grinding wheel, however, requires an interruption of operation and labor time.
With these known sharpening machines for saws, it is possible to grind faces slanting on one side or on alternate sides in one single revolution of the saw blade and/or to grind chamfered cutting edges. Similarly, it is possible to grind flanks at the back of the teeth and to chamfer the backs of the teeth in one single revolution. However, it is not possible to combine the grinding of faces having a positive rake angle with the grinding of flanks and/or faces having a negative rake angle in a time-saving manner, e.g., in one single revolution.
Another sharpening machine for saws is known and disclosed in a catalog (WIDMA-HKS-750) issued by H. E. Widmann gmbH and Company KG,D-7902 BLAUBEUREN in which two entirely separate grinding units are connected to a common machine frame through a swiveling device and a lifting device for each unit. The machine successively grinds the face on the cutting edge and the flank at the back of a tooth. The grinding unit for the faces is disposed on a transverse carriage, which has to be moved a considerable distance away from the saw blade before the other grinding unit can operate.
Accordingly, it is an object of the present invention to provide a sharpening machine wherein the grinding of faces having a positive rake angle and the grinding of flanks and/or faces having a negative rake angle can be accomplished in an efficient and economical manner.
Another object of the present invention is to provide a saw sharpening machine wherein the grinding of faces having a positive rake angle and the grinding of flanks and/or faces having a negative rake angle can be accomplished in a single revolution of the saw blade.
Still another object of the present invention is to develop a saw sharpening machine with moderate construction outlay and in such a way that the set-up time and idle periods of the machine can be shortened in comparison to the operating time, even when complicated saw toothing is being ground.
According to the present invention, a saw-sharpening machine is disclosed in which:
(a) a second grinding wheel is disposed at the grinding head in offset relationship to the first mentioned grinding wheel; and PA1 (b) the grinding head is reciprocable in relation to the support between an operating position of the first grinding wheel and a corresponding operating position of the second grinding wheel.
The two grinding wheels may be disposed in the grinding head in different forms of offset relationship. The type of motion which the grinding head has to perform for bringing one grinding wheel instead of the other into an operating position differs accordingly. If, for example, the two grinding wheels are disposed axially parallel at the grinding head, a rectilinear movement of the grinding head at right angles to the grinding wheel axes can cause the one grinding wheel to be replaced by the other one, as desired. It is important that, in contradistinction to the saw-sharpening machines known to the prior art, both grinding wheels are constantly ready for use. Further, in contradistinction to the other atypical saw-sharpening machine having two entirely separate grinding units, the two grinding wheels in the invention are disposed at a common grinding head and are connected by the common grinding head to the tiltable carrier by way of a common swiveling device and a common lifting device. The above-mentioned features eliminate a large number of relatively movable members and simplifies the different forms of setting-up work required from case to case.
In a preferred embodiment of the invention, the grinding head is adapted to be swiveled by a second swiveling device about a second swivel axis so as to move between two operating positions. It is expedient if the second swivel axis is oriented parallel to the first swivel axis, and if the second swivel axis intersects both grinding wheel axes at right angles. In this way, the space required for the arrangement and for interchanging the two grinding wheels is kept small.
A further preferred feature of the invention is that the second swivel axis is equidistant from the active faces of both grinding wheels. This feature also serves to reduce the space required for interchanging the two grinding wheels.
In a particularly advantageous further development of the invention, the two grinding wheel axes are in alignment. This enables the two grinding wheels, their mounting and their drive to be arranged in a particularly space-saving manner.